Hydraulic power system for reciprocal movement



March 16, 1965 w. w. MGMULLEN HYDRAULIC POWER SYSTEM FOR RECIPROCALMOVEMENT Filed July 9, 1962 3 Sheets-Sheet 1 March 16, 1965 w. w. MMULLEN 3,173,256

HYDRAULIC POWER SYSTEM FOR RECIPROCAL MOVEMENT Filed July 9, 1962 5Sheets-Sheet 2' NVENTOR 1M4 V/VE M Mam/1.; EN

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HYDRAULIC POWER SYSTEM FOR RECIPROCAL MOVEMENT Filed July 9, 1962 3Sheets-Sheet 5 Fig. .5

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I l I I I I Fz'ge 6 Fig. m F2?- 4 AGO/4 k 34 74A 7 United States Patent3,173,256 HYDRAULIC POWER SYSTEM FOR RECIPRQCAL MOVEMENT Wayne W.McMullen, 1002 67th St., Des Moines, Iowa Filed July 9, 1962, Ser. No.208,396 Claims. (Cl. 60-51) My invention relates to hydraulic cylinders,the circuit in which they function, and the controls therefor, wherebyreciprocal movement of the cylinders and positive control thereof isachieved. This invention is an improvement of my co-pending applicationSerial Number 164,944 filed January 8, 1962.

A principal object of my invention is to provide a hydraulic systemincorporating a control means and a pair of cylinders interconnected ina pair of separate hydraulic circuits whereby one circuit can support agiven load and the other circuit can be used to induce reciprocalmovement to the load.

A further object of my invention is to provide a hydraulic power systemfor reciprocal movement wherein the reciprocal movement can beadjustably varied and controlled.

A still further object of my invention is to provide a hydraulic powersystem for reciprocal movement wherein movement of the load involved inone direction is slowed, stopped and thence reversed by accumulatorswithin the various hydraulic circuits.

A still further object of my invention is to provide a hydraulic powersystem for reciprocal movement which can automatically compensate forfluid losses in the load supporting circuit.

A still further object of my invention is to provide a hydraulic powersystem for reciprocal movement that will provide a smooth transition ofpower to the load involved as the movement thereof is being reversed toreduce wear on both the power equipment and the components of the loadbeing moved.

A still further object of my invention is to provide a hydraulic powersystem for reciprocal movement wherein a plurality of loads can beintermittently reciprocated.

A still further object of my invention is to provide a hydraulic powersystem for reciprocal movement wherein a plurality of loads can beintermittently reciprocated while being located at remote locations.

A still further object of my invention is to provide a hydraulic powersystem that is economical to manufacture and durable in use.

These and other objects will be apparent to those skilled in the art.

My invention consists in the construction, arrangements, andcombination, of the various parts of the device, whereby the objectscontemplated are attained as hereinafter more fully set forth,specifically pointed out in my claims, and illustrated in theaccompanying drawing, in which:

FIGURE 1 is a vertical sectional view of one of my hydraulic cylinders;

FIGURE 2 is a plan view of one of my cylinders mounted on a derrickstructure with the yoke of a pump mounted thereon;

FIGURE 3 is a plan view of another of my cylinders similarly situated asthe cylinder in FIGURE 1 but with the hydraulic controls attachedthereto;

FIGURE 4 is an elevational view of the cylinders shown in FIGURES 2 and3 with interconnecting hydraulic conduits schematically arranged;

FIGURES 5, 6, 7 and 8 are partial elevational views of the two cylindersdepicted in FIGURE 4 and show the relative positions of the controlelements as the depleted of fluid;

FIGURE 10 is a side elevational view of the cam control surfaces on mydevice;

FIGURE 11 is a front elevational view of the cam control surfaces on mydevice;

FIGURE 12 is a sectional View through one of my accumulators when thefluid has been exhausted therefrom; and

FIGURE 13 is a view similar to that of FIGURE 12 when the diaphragm ofthe accumulator has been filled with fluid.

I have used the numeral 10 to generally designate an outer base cylindercomprised generally of a flat bottom portion 12 and vertical side walls14. Apertures 16 in the protruding edges of bottom portion 12 can beused to facilitate the connection of cylinder 16 to a supporting surface18.

A vertical bore 26 is located in the center of bottom portion 18 and anupwardly extending shoulder 21 appears at the upper end thereof. Groove22 is formed at the upper inner periphery of shoulder 21. Bore 20receives the lower end of vertical shaft 24 which is shaped to rest ongroove 22 before terminating in the lower portion of bore 29. Shaft 24is rigidly secured to cylinder 16 in any convenient manner such as by athreaded connection. A shoulder 28 extends outwardly from shaft 24 at apoint just below its upper end. The center bore 29 of a stationarypiston 30 receives the extreme upper end of shaft 24 whereby the pistonrests on the shoulder 28 of the shaft. A threaded bore 32 appears in thecenter of the upper end of shaft 24. Shaft 34 has a diameter equal tothat of shaft 24. A shoulder 36 similar to shoulder 28 on shaft 24extends outwardly from shaft 34 at a point just above the threaded lowerend of shaft 34. The threaded lower end of shaft 34 is received in thecenter bore 29 of piston 30 and is threadably received within thethreaded bore 32 in the upper end of shaft 24. Thus, the piston 30 isheld in a stationary position between the similar shoulders 28 and 36 oftwo similar shafts 24 and 34, respectively. Shaft 34 extends upwardlyfrom piston 3t? and can have stop elements 38 detachably secured to itsupper end in any convenient manner.

A movable inner cylinder 40 having an outside diameter substantiallyequal to the inside diameter of base cylinder 10 is slidably mountedwithin and projecting from the upper end of cylinder 10. Cylinder 40 iscomprised generally of a bottom portion 42 which is connected in anyconvenient manner such as by threads to vertical side walls 44 and a topportion 46. A flange 48 is secured to and protrudes outwardly from topportion 46 and apertures 59 therein to facilitate the attachment of theflange to an object or component part of related equipment which is tobe forcibly moved. A vertical bore 52 in bottom portion 42 of cylinder40 slidably receives shaft 24. Sirnilarly, vertical bore 54 in thecenter of top portion 46 of cylinder 40 slidably receives shaft 34.Sealing elements 56 and 58 effect a seal between cylinder 40 and shaft34; elements 60 and 62 effect a seal between piston 30 and cylinder 40;

sealing ring 64 mounted on the upper periphery of cylinder 4!) assistsin effecting a seal between cylinders 10 and 40, as does sealing ring 66on the lower end of cylinder 40; and elements 68 and 70 effect a sealbetween the lower end of cylinder 40 and shaft 24.

As shown in FIG. 1, a hydraulic fluid compartment '72 is formed betweenthe bottom portions of the two cylina ders and 40. A second hydraulicfluid compartment 74 is located between stationary piston and the bottomportion 42 of inner cylinder 49. A third hydraulic fluid compartment 76is located between stationary piston 30 and the upper portion 46 ofinner cylinder 40.

A port 78 in the upper portion 46 of cylinder communicates withpassageway 80 which in turn communicates with fluid compartment 76. Aport 82 in the bottom portion 12 of cylinder 10 terminates in passageway84 which in turn registers with passageway 86 in shaft 24. The upper endof passageway 86 communicates with fluid compartment 74. Port 88 in thelower portion of cylinder 10 communicates directly with fluidcompartment 72.

In FIGURE 4, I have shown pairs of the hydraulic cylinder justdescribed, and the second cylinder in each of these figures will havethe letter A following the numeral identification of its component partsso that, for example, shaft 34 in one cylinder will correspond to shaft34A in the other cylinder. with supporting surfaces or platforms 18,support the cylinders 10 and 10A. The respective cylinders can besecured to platforms 18 by inserting appropriate fastening means throughapertures 16 and 16A in the bottom portions of each cylinder. Yokes 92and 92A respectively include horizontal bars 94 and 94A which aresecured to the upper surfaces of cylinders 40 and 48A by bolt and nutassemblies 96. Vertical hanger bars 93 and 198, and 98A and 100A, aresecured to the ends of bars 94 and 94A, respectively, and extenddownwardly therefrom. The hanger bars slidably extend through suitableopenings (not shown) in platforms 18. The lower ends of the hanger barson each cylinder are joined by conplings 102 which can be operativelyconnected to an oil pumping mechanism located beneath each derrick. Theoil pumping mechanism is associated with an oil well usually locateddirectly below each derrick.

An oil reservoir 104 is mounted in any convenient fashion on theplatform 18 of derrick 90A and contains a hydraulic pump 106 which inturn is connected to a convenient source of electrical power or the like(not shown). A conventional switch (not shown) can control the operationof pump 106. A bracket 108 is secured to the top of reservoir 164 andvalve means 110 is rigidly secured to the top of the bracket. A conduit112 connects pump 106 with a pressure port in valve means 110.

Two parallel arms 114 and 116 are pivotally secured to bracket 108 andextend towards hanger bar 109A on yoke 92A. A wheel 117 is rotatablymounted on the outer end of each of the arms. Two control rods 114A and116A are slidably mounted in and extend out of valve means 110 to bepivotally connected to arms 114 and 116, respectively, at pointseccentric to the point of pivotal connection between the arms andbracket 108. Rods 114A and 116A are spring loaded within valve means 110to normally yieldably hold the arms 114 and 116 in the horizontalposition shown by arm 116 in FIGURE 4. Three conduits, 118, and 122extend away from valve means 110. The rod 116A and arm 116 are adaptedto withhold the flow of hydraulic pressure to conduit or line 118 whenarm 116 is in horizontal position shown in FIGURE 4, but are adapted topermit the flow of fluid into the line 118 when arm 116 is depressed asshown in FIGURE 9. The arm 114 and rod 114A are adapted to withhold theflow of hydraulic pressure to lines 120 and 122 whenever arm 114 is inthe horizontal position shown in FIGURES 5 and 7; but to permit the flowof fluid under pressure to one of the lines 120 and 122, respectively,when arm 114 is moved either upwardly or downwardly as will be explainedhereafter.

A hydraulic conduit or line 124 connects ports 88 and 88A on cylinders10 and 10A to interconnect compartments 72 and 72A. Line 118 isconnected to line 124 to conduct fluid to or from the compartments 72and 72A. Line 120 extends from valve means 110 to port 82A of Derricks98 and 90A,

cylinder 10A to convey fluid to and from compartment 74A. Line 120 isalso connected to port 78, and hence to compartment 76 in cylinder 49,by line 126. Line 120 is also connected to accumulator 128 by line 139.Accumulators 128 and 132 are comprised of closed tanks 134 into which asealed expandable diaphragm 136 is inserted. The diaphragms 136 areconnected to the incoming hydraulic fluid lines through fittings 138.The tanks 134 normally contain a highly compressible gas such asnitrogen which can be inserted into the tanks through normally closedvalves 140. Line 122 extends from valve means 119 to port 82 on cylinder16 to be in communication with fluid compartment 74. Line 122 is alsoconnected to port 78A on cylinder 40A by line 142 to be communicationwith compartment 76A. Line 144 connects line 122 with the diaphragm 136of accumulator 134.

As shown in FIGURES 10 and 11, a rectangular plate 146 with fourvertical slots 148 in the corners thereof is mounted on the side ofhanger bar 169A adjacent the arm 114 on valve means 110. Plate 146 issecured to bar 100A by four adjustable bolts 150 which extend throughthe slots 148. Thus, the vertical position of plate 146 can be adjustedon bar A by loosening the bolts 156, moving the plate vertically byvirtue of slots 148, and then re-tightening the bolts. Similarly, plate152 having vertical elongated slots 154 is adjustable secured to plate146 by stud bolts 156 which extend out of plate 146 through slots 154.An elongated vertical shoulder 158 extends outwardly from plate 152 andis of integral construction with the plate. The lower end of shoulder158 is arcuate to present a cam surface. A second elongated verticalshoulder 160 extends outwardly from plate 146 and is of integralconstruction with the plate. The upper end of shoulder 160 is arcuate topresent a cam surface, and the lower end thereof terminates in tongue162 which is slidably inserted into slot 164 in shoulder 158, wherebythe combined lengths of shoulders 158 and 166, which form a combined camshoulder designated as 159, can be varied.

A plate 168 having vertical corner slots 178 is adjustably secured tobar 100A by bolts 172 in the same manner as was plate 146, but at apoint on bar 100A above plate 146 and vertically opposite arm 116 onvalve means 110. A vertical shoulder 174 extends outwardly from plate146 and is of integral construction therewith. The upper and lower endsof shoulder 174 are arcuate to present a cam surface.

The normal operation of my device is as follows: The pump 106 can beactuated to force hydraulic fluid under pressure through line 112 tovalve means 110. Arm 116 on valve means 110 can then be manuallydepressed to permit fluid to flow into line 118, thence line 124, andthence into the fluid compartments 72 and 72A in cylinders 10 and 10A,respectively. Obviously, arm 116 could be electrically actuated by asolenoid in valve means 110 if the Valve were so designed, but since theprecise components of valve means are of conventional structure, I havenot shown it in great detail. The introduction of fluid intocompartments 72 and 72A exerts an upward force on the bottoms ofcylinders 40 and 40A, and these cylinders will uniformly rise andsupport the entire load imposed on the cylinders by the yokes 92 and92A. When arm 116 is permitted to assume a horizontal position, rod 116Awillclose to prevent further fluid from entering the conduit 118, andhence the compartments 72 and 72A. If desired, the arm 116 can be movedupwardly to by-pass the pressure port in valve means 110 whereby theweight on cylinders 40 and 40A will force the fluid out of compartments72 and 72A as these compartments are reduced in volume, whereupon theflow of fluid in this circuit will be reversed and returned directly tooil reservoir 104 by means of a return line 176 extending downwardlyfrom valve means 110 to the reservoir.

The oil well pump mechanism referred to above will require a reciprocalvertical movement of each yoke 92 and 92A. After the yokes have beenraised to a satisfactory minimum elevation by introducing fluid intocompartments 72 and 72A, the arm 114 on valve means 110 may be in aneutral horizontal position whereby no fluid would be forced into lines120 or 122, and the elevations of the yokes (and hence, cylinders 40 and413A) would be fixed by the fluid then in lines 120 and 122 beyond valvemeans 110. With the cylinder 40 and 40A at the same elevation shown inFIGURE 4 as pump 196 is actuated, arm 116 is pivoted upwardly by camshoulder 159 (comprised of shoulders 153 and 1nd) to introduce fluidunder pressure into conduit 122, thence through line 142 intocompartment 76A, and also into compartment 74. At the same time, fluidmoves into the diaphragm 136 of accumulator 132 to cause the diaphragmto inflate and compress the gas within tank 134. Since piston 311A willnot move, the introduction of fluid into compartment 76A will forcecylinder 411A upwardly. Similarly, since piston 30 cannot move, theintroduction of fluid into chamber 74 will cause cylinder 41 to movedownwardly. Fluid initially in compartment 74A is thereupon flushed outthrough conduits 121i and 126 towards compartment 76. This flow of fluidwould ordinarily impede the desired result except that the fluid flowingthrough conduit 129 towards compartment 76 will also be partiallyexhausted through conduit 120 between conduit 126 and valve means 110back towards reservoir 104. This discharge of fluid from line 120, inaddition to the gas pressure in the tank of accumulator 123, will causethe diaphragm 136 therein to become deflated. Thus, during this cycle ofthe operation, yoke 92 will be moving downwardly with cylinder 40, andyoke 92A will be moving upwardly with cylinder 49A.

However, as the yoke 92A and hanger bar ltltlA thereof move upwardly tothe degree shown in FIGURE 5, the arm 116 will move out of engagementwith cam shoulder 159 and will move into a neutral position wherein nofluid is allowed to flow into or out of lines 1211' or 122. However, thegreat pressure being exerted on the outside of the fluid filleddiaphragm 136 by the compressed gas in tank 134 of accumulator 132 willcause fluid to flow out of the diaphragm towards both compartments 7 6Aand 74. Thus, the upward and downward movement of cylinders 40A and 40,respectively, will still continue at a reduced rate of speed. At thesame time, the diaphragm 136 in accumulator 128 will start to becomeinflated because the fluid being flushed out of compartments 76 and 74Acannot return to the reservoir 1194. As the diaphragm in accumulator 132becomes increasingly deflated, and the diaphragm in accumulator 128becomes increasingly inflated, the accumulator 128 will then takecontrol of the circuit, stop the movement of the cylinders 40 and 411A,and reverse their initial movernent whereupon cylinder 41? will start tomove upwardly, and cylinder 40A will start to move downwardly. This isaccomplished by the gaseous pressure in the tank of accumulator 123forcing oil out of the then inflated diaphragm therein, wherein fluidwill be forced into chambers 74A and 76 to reverse the initial movementof the cylinders. At the same time, the diaphragm in accumulator 132 isbeginning to become inflated again.

As the cylinder MA and yoke 92A move downwardly, cam shoulder 15? againcomes into contact with arm 114 to pivot it to the depressed positionshown in FIGURE 6. This immediately causes fluid under pressure to flowinto line 120 to continue the upward and downward movement of cylinders40 and 49A, respectively, which was already started by pressurized fluidin accumulator 123.

As the downward movement of cylinder 411A and yoke 92A continues, a camshoulder 159 disengages arm 114 which moves to its neutral horizontalposition in which fluid is prevented from entering or leaving the lines120 and 122 at valve means 110. At this point, the diaphragm 136 inaccumulator 132 becomes inflated as the pressurized fluid in theaccumulator 128 continues the movement of the cylinders. Finally, thepressure within the accu mulator 132 stops and reverses the movement ofthe cylinders in the same manner that the pressure in accumulator 128served this function at the first part of the cycle. The reversal ofmovement of the cylinders 40 and 411A will cause yoke 92A to rise sothat arm 114 is once again elevated by cam shoulder 159 to bring thecycle back to its point of beginning whereupon the cycle will berepeated.

The amount of gas in each of the accumulators 128 and 132 can be variedin the adjustment of the cycle. Similarly, the position and length ofcam shoulder 159 can be altered in the manner described to provideadjust ments in the stroke of the cylinders. If fluid should leak fromthe lower compartments 72 and 72A so that the minimum elevation of thecylinders 41) and 40A, and the yokes 92 and 92A become less than thatinitially determined, the cam shoulder 174 will then come into contactwith arm 116 as shown in FIGURE 9 whereupon the cylinders 40, 441A, andyokes 92 and 92A will be simultaneously raised in the manner describedby the simultaneous introduction of fluid into chambers 72 and 72A. Thevertical position. of shoulder 174 can be adjusted in the mannerdescribed to better control this aspect of the operation.

Thus, from the foregoing, it is seen that my device will accomplish atleast all of its stated objectives.

Some changes may be made in the construction and arrangement of myHydraulic Power System for Reciprocal Movement without departing fromthe real spirit and purpose of my invention, and it is my intention tocover by my claims, any modified forms of structure or use of mechanicalequivalents which may be reasonably included within their scope.

I claim:

1. In combination,

first and second cylinder units, each cylinder unit comprising,

a base cylinder having an open top and a closed bottom portion,

a shaft means rigidly secured to the bottom portion of said basecylinder and extending upwardly and outwardly from the upper endthereof,

a movable cylinder slidably mounted on said shaft means and having atleast one of its ends slidably mounted within said base cylinder,

a piston element rigidly secured to said shaft within said movablecylinder to form separate fluid compartments within said movablecylinder above and below said piston element,

a first conduit connecting the compartment above said piston in saidfirst cylinder unit to the compartment below said piston in said secondcylinder unit,

a second conduit connecting the compartment below said piston in saidfirst unit with the compartment above said piston in said secondcylinder unit,

a hydraulic power means in communication with said first and secondconduits,

a valve means imposed in said conduits to control the flow of fluidthrough said conduits towards or away said compartments at differenttimes by said hydraulic power means,

and an actuating means on said valve means and in the movable path ofone of said movable cylinders whereupon the movement of said one movablecylinder will engage said actuating means to operate said valve means.

2. The structure of claim 1 wherein a third conduit connects the bottominterior portions of said two base means, said third conduit isconnected to said hydraulic power means, and a valve is imposed in saidthird conduit to control the flow of fluid through said third conduittowards or away from said cylinders.

3. The structure of claim 1 wherein accumulators are imposed in saidconduits, said accumulators including means that can yieldably absorbhydraulic pressure.

4. The structure of claim 1 wherein accumulators are imposed in saidconduits, said accumulators including means that can yieldably absorbhydraulic pressure, and means within said accumulators for varying theamount of hydraulic pressure said accumulators can absorb.

5. The structure of claim 1 wherein accumulators are imposed in saidconduits, said accumulators including means that can yeildably absorbhydraulic pressure, and means within said accumulators for varying theamount of hydraulic pressure said accumulators can absorb; saidaccumulators being comprised of a closed tank, a sealed diaphragm ineach of said tanks in communication with one of said conduits, and acompressible gas Within said tanks and outside of said diaphragms.

6. The structure of claim 1 wherein accumulators are imposed in saidconduits, said accumulators including means that can yieldably absorbhydraulic pressure, and means within said accumulators for varying theamount of hydraulic pressure said accumulators can absorb; saidaccumulators being comprised of a closed tank, a sealed diaphragm ineach of said tanks in communication with one of said conduits, and meanson said tank for ad justing the quantity of compressible gas within saidtanks.

7. The structure of claim 1 wherein a cam shoulder is operativelyengaged to one of said movable cylinders, and is adapted to engage saidactuating means to effect the operation of the actuating means, andmeans on said cylinder for adjusting the position of said cam shoulderwithtrespect to said movable cylinder.

8. The structure of claim 1 wherein a cam shoulder is operativelyengaged to one of said movable cylinders, and is adapted to engage saidactuating means to effect the operation of the actuating means, andmeans on said cylinder for adjusting the length of said cam shoulderwith respect to said movable cylinder.

9. The structure of claim 1 wherein a third conduit connects the bottominterior portions of said two base means, said third conduit isconnected to said hydraulic power means, and a valve is imposed'in saidthird conduit to control the flow of fluid through said third conduittowards or away from said cylinders, and a second actuating means onsaid valve means and in the movable path of one of said movablecylinders whereupon the movement of said movable cylinder will engagesaid second actuating means upon a predetermined degree of movement ofsaid movable cylinder to operate the valve means in said third conduit.

10. In combination,

first and second cylinder units, each cylinder unit comprising,

a base cylinder having an open top and a closed bottom portion,

a shaft means rigidly secured to the bottom portion of said basecylinder and extending upwardly and outwardly from the upper endthereof,

a movable cylinder slidably mounted on said shaft means and having atleast one of its ends slidably mounted within said base cylinder,

a piston element rigidly secured to said shaft within said movablecylinder to form separate fluid compartments within said movablecylinder above and below said piston element,

a first conduit connecting the compartment above said piston in saidfirst cylinder unit to the compartment below said piston in said secondcylinder unit,

a second conduit connecting the compartment below said piston in saidfirst unit with the compartment above said piston in said secondcylinder unit,

a hydraulic power means in communication with said first and secondconduits,

a valve means imposed in said conduits to control the flow of fluidthrough said conduits towards or away said compartments at differenttimes by said hydraulic power means,

an actuating means movably secured to said valve means and having threeoperable positions wherein a first position will cause the flow ofhydraulic fluid into only said first conduit, a second neutral positionwill prevent the flow of fluid into or out of either conduit, and thethrid position will permit the flow of fluid into only said secondconduit,

one or" said movable cylinders being a control cylinder,

a cam shoulder operatively secured to said control cylinder and beingpositioned to interimmtcntly engage said actuating means to move saidactuating means :to said first or said third position,

said actuating means normally being in said neutral position upon beingfree from engagement with said actuating means,

the fiow of fluid through said first conduit being adapted to move saidcontrol cylinder in a first direction,

accumulators imposed in each of said conduits, said accumulatorsincluding means that can yieldably absorb, retain and thence dischargehydraulic pressure,

said accumulators absorbing hydraulic pressure when fluid under pressureis introduced into the respective conduits to which said accumulatorsare secured,

the accumulator in said first conduit having a pressure capacity todischarge hydraulic fluid to continue to move said control cylinder insaid first direction after said cam shoulder has released said actuatingmeans from said first position to allow said actuating means to move tosaid neutral position,

fluid in said second conduit responsive to the displacement of saidmovable cylinders by the pressure in said first conduit whereby theaccumulator in said second conduit will absorb hydraulic pressure as theaccumulator in said first conduit discharges hydraulic pressure tocontinue to move said control cylinder in said first direction,whereupon the movement of said control cylinder will be stopped wdreversed as the accumulator in said second conduit absorbs the ydraulicpressure being spent by the discharge of hydraulic pressure from theaccumulator in said first conduit, whereupon said control cylinder andsaid cam shoulder can move into engagement with said actuating means tomove said actuating means from said neutral position to said thirdposition.

References Qited in the file of this patent UNITED STATES PATENTS1,552,768 Smith Sept. 8, 1925 2,110,972 DinZl Mar. 15, 1938 2,172,016.Scheider et a1. Sept. 5, 1939 2,505,771 Hoar et al May 2, 1950 2,555,427Trautman June 5, 1951 2,802,336 Ball Aug. 13, 1957 2,851,994 Fagge Sept.16, 1958

1. IN COMBINATION, FIRST AND SECOND CYLINDER UNITS, EACH CYLINDER UNITCOMPRISING, A BASE CYLINDER HAVING AN OPEN TOP AND A CLOSED BOTTOMPORTION, A SHAFT MEANS RIGIDLY SECURED TO THE BOTTOM PORTION OF SAIDBASE CYLINDER AND EXTENDING UPWARDLY AND OUTWARDLY FROM THE UPPER ENDTHEREOF, A MOVABLE CYLINDER SLIDABLY MOUNTED ON SAID SHAFT MEANS ANDHAVING AT LEAST ONE OF ITS ENDS SLIDABLY MOUNTED WITHIN SAID BASECYLINDER, A PISTON ELEMENT RIGIDLY SECURED TO SAID SHAFT WITHIN SAIDMOVABLE CYLINDER TO FORM SEPARATE FLUID COMPARTMENTS WITHIN SAID MOVABLECYLINDER ABOVE AND BELOW SAID PISTON ELEMENT, A FIRST CONDUIT CONNECTINGTHE COMPARTMENT ABOVE SAID PISTON IN SAID FIRST CYLINDER UNIT TO THECOMPARTMENT BELOW SAID PISTON IN SAID SECOND CYLINDER UNIT, A SECONDCONDUIT CONNECTING THE COMPARTMENT BELOW SAID PISTON IN SAID FIRST UNITWITH THE COMPARTMENT ABOVE SAID PISTON IN SAID SECOND CYLINDER UNIT, AHYDRAULIC POWER MEANS IN COMMUNICATION WITH SAID FIRST AND SECONDCONDUITS, A VALVE MEANS IMPOSED IN SAID CONDUITS TO CONTROL THE FLOW OFFLUID THROUGH SAID CONDUITS TOWARDS OR AWAY SAID COMPARTMENTS ATDIFFERENT TIMES BY SAID HYDRAULIC POWER MEANS, AND AN ACTUATING MEANS ONSAID VALVE MEANS AND IN THE MOVABLE PATH OF ONE OF SAID MOVABLECYLINDERS WHEREUPON THE MOVEMENT OF SID ONE MOVABLE CYLINDER WILL ENGAGESAID ACTUATING MEANS TO OPERATE SAID VALVE MEANS.